Telephone system



Aug. 29, 1939. U.KES1"EN 2,179,903

TELEPHONE SYSTEM Filed May 29, 1956 IN VENTOR. ULRICH I K E5 TEN ATTORNEPatented Aug. 29, 1939 UNITED STATES 2,170,903. TELEPHONE SYSTEM UlrichKesten, Staaken, Germany, assignor to Siemens & HalskeAktiengesellschaft, Berlin,

Germany Application May 29, 1936, SerialNo. 82,390

In Germany June 1, 1935 10 Claims.

The present invention relates to a circuit arrangement for subscriberslines in telephone systems provided with freely hunting switches andmore particularly preselectors. It aims at rendering false callingconditions at the subscribers lines inoperative as regards their effecton the hunting switches in such systems.

False calling conditions can be produced on .account of y the completionof loops of subscribers lines or connecting lines. They can also occurduring the establishment of a connection or during the releasingoperations. In the first case the calling condition produced whensetting up a call may be recognized as false if a subscriber afterinitiating a call delays for a definite period before completing thecall. The second case occurs when in systems in which the release of aconnection is dependent upon the calling subscriber, the final selectorbecomes released before the called subscriber has replaced his receiver.

For the purpose of rendering inoperative the false calling conditionsoccurring in all these cases the arrangement according to the inventionproduces a circuit arrangement which does not involve any furtherexpenditure of switching means at the subscribers lines .and withoutusing special constructional means.

This is achieved in that a two-stage relay brought under the influenceof the subscribers line through the operation of a releasing impulsetransmitted when a false calling condition is set be applied to freelyhunting switches of various constructions for example preselectors orgroup selectors especially since in the case of group seto outgoinglines over the preselector VW. One of these outgoing lines isrepresented by Lal,

Lb! and Lcl. The preselector possesses four wipers which are indicatedby so, sb, so and sd. The wiper sd serves to return the preselector tothe rest position. To contact I l in the contact bank of the testingwiper so a relay G is con-'- nected which is common to severalpreselectors and which controls a time switch which transitorily openscontact 970. It is not necessary to point out the object of thisoperation as it forms no part of the invention. I A two-stage line relayR having windings I, II andIII, is associated 5 with the subscriber Tnat his connectingline. Cut-off relay T having windings I and II isconnected to the subscribers line and serves as a testing relay. ,Whenenergized in its first stage (winding I) relay R, operates only thecontact 81*. When fully energized i. e. over winding III the relayoperates contacts 51', 61" and Tr. Winding II of relay R serves as alocking winding and maintains the relay energized in the second stage. a

.When the subscriber at the station Tn initiates a call the followingcircuit is established on the removal of the receiver: earth, battery,resistance Wi, contact It, lead La, loop at the subscribers station Tn.lead Lb, contact 2t, winding I of relay R, contact 51', and earth. Inthis circuit relay R energizes in the first stage. It accordinglyoperates contact 81' so that the following stepping circuit isestablished for the preselector: earth, battery, wiper sd, position 0 ofwiper sd, contacts 81", 3t, 17', rotary magnet DVW, interrupter RU andearth. The rotary magnet DVW is energized impulsivel-yin this circuit.When the preselector findsa free line for example the line Lal, Lbl, Lcl, shown, the following testing circuit is set up: earth, battery, wipersd, contact 81', windings II and I of relay T, winding III of relay R,contact 61", wiper so, lead Lcl, contact Hit?" of a thermal relay TR,switching means (not shown) in the subsequently arranged switchingdevices,vrelay TR, and earth. In this circuit relayT energizes while thecurrent flowing through relay TR heats the thermostatic elementassociated therewith, to cause the operation of contact n after apredetermined time. By switchingover'contact it the testing circuit ismaintained. Bythe switching over of contact 3t the stepping circuit isbroken and thus the preselector is brought to rest. In the circuit justmentioned relay R becomes fully energized over its winding IIIJ It thenoperates contacts 51', 61' and 11'. This, however, does not produce anyparticular switching operation.

It may be mentioned that .a meter can be arranged in parallel withwinding I of relay T.

If the subscriber now operates his calling device to operate theswitching mechanism connected to line conductors Lal, Lb I, Lcl, theinitial movement of the switch closes contacts. onl, which remain closedas long asthe switch is offnormal, to short circuit relay TR and tothereby prevent the opening of contacts llltr.

If the subscriber does not continue the further establishment of theconnection within a given period, for example, by delaying the diallingoperation, the contact Illtr is momentarily opened. This has the effectof breaking the circuit passing over wiper so and winding I of relay T.Relay T releases and returns its contact to the normal position. Theswitching over of contact 315 does not, however, establish the steppingcircuit for the preselector since contact 11' is still open. On thereturn of contacts It and 272 to the rest position the following circuitis established: earth, battery, resistance Wi, contact It, lead La, loopat the subscribers station Tn, lead Lb, contact 213, windings I and IIof relay R and earth. In this circuit relay R remains fully energized.Contacts 5T, 61' and Ir are accordingly in the working position. Theline originally seized is again accessible to general trafiic since theseizing circuit is broken at contacts 4t and 61.

The subscriber can now be given a signal in any known manner indicatingthat he has become disconnected. When he replaces his receiver relay Rreturns to normal and contact 11" reestablishes the stepping circuit,whereupon the preselector is advanced until its wipers have reached therest position, i. e., when wiper sd reaches contact 0. Testing duringthe return to the rest position is: prevented by the fact of contact 81having been opened on the release of relay R.

It will be assumed that on initiating a call on the part of subscriberTn all the outgoing lines are engaged. In this case the preselector isadvanced to position I I. In this position the following circuit isestablished: earth, battery, wiper sd, contact 8r, windings II and I ofrelay T, winding III of relay R, contact 6r, wiper 80, position H ofwiper so, the common relay G, contact 9k and earth. In this circuitrelay T energizes and switches over its contacts. In addition relay R isenergized completely. Relay G connects up a device which causes contact9k to be transitorily opened. This causes relay T to release so thatrelay R is brought under the influence of the calling station by way ofits windings I and II. Relay R is maintained energized completely overthe subscribers loop so that the testing circuit is broken at contact61' and the stepping circuit is broken at contact Ir. The preselectoraccordingly remains in position I I until the calling subscriberreplaces his receiver and thus releases relay R. Guarding of contact lldoes not take place during the disconnecting condition on account of theopening of the testing circuit at contacts 4t and Br. When thesubscriber replaces his receiver the preselector returns to the normalposition in the manner already described.

The arrangement illustrated can also be used in systems in which therelease of a connection is effected by the calling subscriber in such away that thefinal selector also is returned to normal. Assuming thatsubscriber Tn is called a circuit is established over the incomingtesting line Lcn which passes over resistance Wil wiper so in its restposition, contact 61*, winding III of relay R, windings I and II ofrelay T, wiper sd, battery and earth. In this circuit relays T and R areenergized. Relay T energizes before relay B, so that no stepping circuitis established over contacts 81" and 3t. If the release is effected bythe calling subscriber the earth connected to the lead Lon isdisconnected in any known manner. Relay T accordingly deenergizes. RelayR which is constructed as a slow to release relay does not yet release,but remains energized over the subscribers loop of the called subscriberTn. No stepping of the selector takes place since the stepping circuitwhich is prepared by contact 81' remains broken at contact 11'. When thesubscriber replaces his receiver relay R is deenergized and contacts 8r,H, 61' and 51' return to normal.

What is claimed is:

1. In an automatic telephone system, an automatic switch having accessto a plurality of trunk lines, a cut-off relay and a two-step line relayin said switch, means responsive to the initiation of a call foroperating said line relay in its first step, means controlled by saidline relay in its first step to operate said switch to find an idletrunk line, means for operating said line relay in its second step andalso said cut-off relay when an idle line is found, and means forautomatically deenergizing said cut-oil relay while holding said linerelay fully operated in the event that dialling over the seized trunkline is delayed.

2. In an automatic telephone system an. automatic switch having accessto trunk lines, a two-step line relay in said switch, means responsiveto the initiation of a call for operating said line relay in its firststep, means controlled by the operation of said line relay in its firststep for controlling the operation of said switch to hunt for an idletrunk line, means for operating said line relay in its second step whenan idle trunk line is found, a cut-off relay in said switch, saidcut-01f relay operated responsive to the selection of a trunk line toextend the calling line thereto, means in said trunk line automaticallyoperated in case the subscriber delays dialling for releasing saidcut-off relay and for maintaining said line relay operated, and circuitconnections controlled by the restored cut-off relay and operated linerelay for rendering said trunk line accessible to other switches andlocking said calling line out of service.

3. In an automatic telephone system, a subscribers line circuitincluding a line relay and a cut-off relay individual thereto, anautomatic switch operable responsive to the operation of the line relaywhen a call is initiated over the line for extending said line, a timingdevice associated with said switch effective in the event the callingsubscriber delays dialling, said line relay arranged to operate part wayonly pursuant to the initiation of a call, means for operating said linerelay fully when the cut-off relay operates in response to the extentionof the line, and means responsive to the operation of said timing deviceand depending upon said line relay having been operated fully when theline is extended to lock the subscriber's line out of service.

4. In an automatic telephone system, a subscribers line circuitincluding an automatic switch individual thereto having a cut-off relayand a two-step line relay, means responsive to the initiation of a callfor operating said line relay in its first step to control the operationof said switch to find an idle trunk line and extend the call, means foroperating said cut-off relay and for operating said line relay in itssecond step when the switch finds an idle trunk, means in said selectedtrunk line efiective in case the subscriber fails to dial over the trunkline for deenergizing said cut-ofi relay, and means for maintaining saidline relay fully operated over said line circuit and to release saidtrunk line for service and lock out said line circuit from service.

5. In an automatic telephone system as ill iii

claimed in claim 4 in which the operating circuit for the switch iscontrolled jointly by the cut-oif relay and the line relay and thecircuit is prevented from being efiective when the line is locked out ofservice by the restoration of the cut-off relay and the operation of theline relay, said line relay arranged to be slow acting and held operatedover the subscribers line after the cut-off relay restores.

6. In an automatic telephone system as claimed in claim 4 in which thetesting circuit for the switch in its operation of hunting an idle trunkline is controlled jointly by the cutoff relay and the line relay in itsfirst step, said testing circuit rendered ineifective responsive to thedeenergization of said cut-off relay and the full operation of the linerelay over the line circuit at a time when the line circuit is lockedout.

7. In an automatic telephone system as claimed in claim 4 in which theline circuit is also accessible to incoming calls, means for energizingsaid line relay initially in its second step and said cut-oil relayresponsive to an incoming call, means responsive to the release of. theincoming call for deenergizing said cut-off relay, and means formaintaining said line relay fully operated over said line circuit aftersaid cut-off relay deenergizes, said line relay arranged to be slowacting so as to remain operated during the interval in which the cut-offrelay restores and connects the line relay to the line circuit.

8. In an automatic telephone system as claimed in claim 4 in which theline relay is arranged to be slow acting and is provided with aplurality of windings, one of. said windings serving to energize therelay in its first step when a call is initiated, and another Windingserving to energize the relay in its second step when the call isextended.

9. In an automatic telephone system, a subscribers line circuitincluding an automatic switch individual thereto having a cut-off relayand a two-stage line relay, means responsive to the initiation of a callfor operating said line relay in its first stage, means controlledthereby for operating said switch to find an idle trunk line to extendthe call, means responsive to the switch encountering an idle trunk linefor operating said cut-oil relay and for operating said line relay inits second stage, means for operating said switch to a particularposition in case all trunks are busy, and means connected to the saidparticular position on which the switch stops for deenergizing saidcut-off relay, said line relay remaining fully operated over the linecircuit to lock out the line from service.

10. In an automatic telephone system as claimed in claim 9 in which theline relay in its second stage controls the circuit of the switch fortesting-the condition of the trunk lines and also the operating circuitof the switch, means responsive to the full operation of said line relaywhen the particular position of the switch is reached and all trunklines are busy for disconnecting the testing and operating circuits ofthe switch, and means for deenergizing said line relay responsive to thedisconnection of the calling subscriber and for restoring said switch tonormal position.

ULRICH KESTEN.

